For the manufacture of finished concrete parts, formwork elements are placed onto steel tables and are retained in position by means of anchoring magnet devices placed on the steel table. An anchoring magnet device of this kind is known, for example, from DE 201 05 709 U1.
The anchoring magnets used for such anchoring magnet devices are constructed in plate fashion—i.e. are assembled alternatingly from a plurality of panel-shaped and rectangular magnet elements extending in parallel fashion and soft magnetic pole elements, likewise panel-shaped and rectangular, extending parallel thereto—and are clamped to one another to form an assemblage. Anchoring magnets of this kind are known, for example, from DE 44 24 447 and DE 94 11 585 U1. The pole elements project beyond the magnet elements usually on all end faces, but at least on the underside intended for placement onto the steel table, so that grooves whose bottoms are formed by the end faces of the magnet elements are produced between the pole elements.
The materials used for the magnet elements have little corrosion resistance. To protect them, DE 198 10 612 C2 proposes encapsulating the anchoring magnets in a plastic sheathing material forming a protective layer so that only the pole elements (and in fact only those on the underside of the anchoring magnet) are exposed, the anchoring magnet, and thus in particular the magnet elements, otherwise being completely enclosed. In a variant of this protective feature, only the above-described grooves between the pole elements are encapsulated with a plastic constituting a protective layer, thus protecting the magnet elements from corrosive influences.
Anchoring magnets of this kind rapidly become soiled with splashes of concrete, which adheres tenaciously to the anchoring magnet and is removed mechanically using steel brushes. The result is that the plastic protective layers are gradually removed, with the result that the corrosion-sensitive magnet elements become exposed and corrode.
Known in the existing art as an alternative thereto are anchoring magnets in which several magnet elements embodied as round disks are inserted loosely next to one another into matching receptacles of a protective frame, and the combination of protective frame and magnet elements is clamped between pole elements. The protective frame is made of aluminum or a plastic such as polyethylene. Manufacture of the protective frame is costly. In addition, circular magnetic elements arranged next to one another have poorer effectiveness than rectangular magnet elements.
A further problem is presented by the circumstance that anchoring magnets are required in different sizes. If the magnet elements are rectangular in shape, they must be individually adapted to the particular length of the anchoring magnet. Although this is not necessary in the case of circular magnet elements, the protective frame must nevertheless be equipped with a number of receptacles corresponding to the length of the anchoring magnet, i.e. in that respect once again an individual adaptation must be made. In both cases this results in considerable cost.